In hemodialysis operations, the blood of a patient suffering from impaired kidney function is conducted along one side of a permeable membrane in a dialyzer device, at the same time as dialysis fluid is conducted along the opposite side of the same membrane. The poisons or other waste substances that are to be removed from the blood pass with the help of diffusion from the blood of the patient to the dialysis fluid through the permeable membrane. Normally, a certain amount of fluid, primarily water, is also withdrawn from the blood so as to bring about a lowering of the weight of the patient.
Hemodiafiltration differs from hemodialysis first and foremost in that a more permeable filter membrane is utilized, Consequently, greater ultrafiltration or withdrawal of fluid from the body is obtained, which makes it necessary for a part of the ultrafiltrate removed to be replaced by a replacement fluid. Hemofiltration differs from hemodialysis and hemodiafiltration in that no dialysis fluid is utilized on the opposite side of the permeable membrane along which the blood is conducted. Instead, with the help of a filter, a large quantity of ultrafiltrate is withdrawn from the blood across the filter membrane, which has to be replaced at least partly by a corresponding quantity of replacement fluid.
Different types of control systems are normally used for hemodialysis, hemodiafiltration and hemofiltration operations, respectively. However, they all have in common that at least one concentrate fluid is mixed with pure water in order to produce either the dialysis fluid in connection with hemodialysis operations, or the replacement fluids in connection with hemodiafiltration and hemofiltration operations. Normally, the concentrate to be mixed with water is prepared in centralized preparation plants and is then transferred to the point of treatment in large kegs or other containers. Alternatively, the concentrate may be prepared directly on the spot in large tanks or the like before the treatment is to be started. Thus, in either instance, the concentrate to be used in the medical treatment is prepared in the form of a solution prior to actual use in connection with the medical treatment. At the time of treatment, the concentrate soultion is then mixed with water to provide the desired prepared solution for the particular medical treatment.
Examples of previously used concentrates, in either powder or liquid form, for use in preparing such prior art concentrate solutions may be found, for instance, in U.S. Pat. Nos. 3,560,380; 4,404,192; European Patent Specification Ep-B1-0 022 922; Eurpean Patent Application Nos. EP-A1-0 034 916; EP-A1-0 177 614; and PCT Publication No. WO85/03435. Further, U.S. Pat. No. 4,158,034 describes an example of how such concentrate solutions prepared beforehand can be used in the preparation of a solution suitable for dialysis operations.
Major problems can arise with such prior art types of concentrate solutions prepared prior to their utilization in connection with medical procedures due to the fact that certain concentrates do not always remain stable and/or bacteria-free if prepared in large quantities beforehand. For instance, precipitation may occur either during the transport of concentrate solutions from centralized preparation plants, or even in the aforementioned large tanks or the like before actual treatment is to begin. Furthermore, preparation of concentrate solutions before actual usage in connection with medical treatment can result in bacteria growth if allowed to stand for substantial periods of time.